To confirm some assumptions:
- You've run the normal SSD1351 'test' example (with dc/cs/rst pins adjusted to match wiring) and this works?
- You did NOT install the Adafruit_GFX or Adafruit_SSD1531 libraries offered by the Teensyduino installer? Use the Arduino Library Manager instead or fetch the code from Github. The Teensyduino versions may break something. Remove them if that's what you installed.
- You're running the plain vanilla Uncanny Eyes sketch linked to in the guide, not anyone's custom variant just yet, correct?
- Using the default human eye?
- Teensy speed set at 72 MHz?